Golf Ball Core Negative Hardness Gradient Trans-Polybutadiene
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Solution Overview
Problem
There is a need for a single layer golf ball core that exhibits a soft-to-hard hardness gradient from the surface to the center, which is both inexpensive and efficient to produce, allowing for unique combinations of compression, feel, and spin.
Innovation Solution
A golf ball with a unitary core formed from a substantially homogeneous rubber composition, featuring a soft transition region with up to 4 mm thickness and 8-20% trans-polybutadiene isomer, providing a negative hardness gradient of up to 15 Shore C, and a core with a geometric center and outer surface hardness gradient defined by the equation G+T10×COR≤7, where G is the overall negative hardness gradient, T is the percent of trans-polybutadiene isomer, and COR is the coefficient of restitution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional hard surface to soft center hardness gradient is used in the core, then the manufacturing process is simple, but the golf ball lacks unique combinations of compression, feel, and spin properties
Solution Approach 1:
The patent applies local quality by creating distinct regions within the core with different hardness characteristics. The core includes a soft outer transition volume (0-4mm from surface) with 8-20% trans-polybutadiene isomer, a medium hardness intermediate volume (4-8mm from surface) with 5-15% trans-polybutadiene isomer, and a hard center volume (>8mm from surface) with 0-10% trans-polybutadiene isomer. This regional differentiation provides customized compression, feel, and spin properties while maintaining a unitary structure that can be manufactured efficiently through controlled curing processes.
2Manufacturing precision
If a soft outer transition volume with negative hardness gradient is created, then unique hardness profiles are achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent utilizes parameter changes by controlling the trans-polybutadiene isomer content at different radial distances from the core surface (8-20% in outer transition, 5-15% in intermediate, 0-10% in center) and adjusting curing parameters (temperature, time, catalyst distribution) to create the negative hardness gradient. This approach achieves precise hardness gradient control (10-30 Shore C difference between surface and center) while using a unitary core structure that can be manufactured through modified conventional curing processes rather than complex multi-step assembly.
3Manufacturing precision
If multiple elastomers are mixed to create hardness gradient, then the desired hardness profile is achieved, but the manufacturing process is time-consuming
Solution Approach 1:
The patent applies segmentation by dividing the core into functional volumetric regions (outer transition volume 0-4mm, intermediate volume 4-8mm, center volume >8mm) with progressively different trans-polybutadiene isomer concentrations. This segmentation achieves the desired hardness gradient through compositional variation within a single unitary core structure, allowing efficient one-step curing manufacturing rather than time-consuming multi-step assembly of separate elastomer layers. The segmented regional composition can be achieved through controlled mixing and curing processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables the creation of golf balls with a unique hardness profile that balances compression and spin, achieving a high coefficient of restitution and customizable properties, enhancing the golf ball's performance and manufacturing efficiency.
Implementation Method 1
The soft transition region also has a negative hardness gradient of up to 15 Shore C
Implementation Method 2
The unitary core has an overall negative hardness gradient of up to 20 Shore C and has a gradient quotient, GQ, defined by the equation: G+T10×COR≤7, where G is the overall negative hardness gradient, T is the percent of trans-polybutadiene isomer, and COR is the coefficient of restitution
Data Source
AI summary
A golf ball includes a unitary core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface, and is formed from a substantially homogenous composition. The ball further includes an outer cover layer. The soft transition region has a thickness of up to 4 mm, has about 8 to 20 percent trans-polybutadiene isomer, and has a negative hardness gradient of up to 15 Shore C. The core has an overall negative hardness gradient of up to 20 Shore C and has a gradient quotient, GQ, defined by the equation:G+T10×COR≤7where G is the overall negative hardness gradient in Shore C, T is the percent of trans-polybutadiene isomer at the core outer surface, and COR is the coefficient of restitution measured at an incoming velocity of 125 ft/s.